The following embodiments of the inventive concept relate to a printed-circuit board (PCB) structure having an electromagnetic (EM)-tunnel-embedded architecture which is an electromagnetic waveguide and a method for manufacturing the same, and more particularly to a technology of transmitting electromagnetic signals through an EM-tunnel-embedded in a PCB by embedding an EM-tunnel including at least one horizontal part and at least one vertical part in the PCB.
Substrates suitable for high-capacity/high-speed data processing have been required in high-performance computers or communication systems. Accordingly, the densely-integrated PCB technologies which use a multilayered circuit having a high density of metal connection lines have been developed as substrate technologies for high-capacity/high-speed data processing, but signal loss becomes severe in micro-strip signal lines of metal connection line and an electromagnetic interference between adjacent signal lines increases as data transmission speed increases. In particular, most of signal losses in high-density multilayered connection lines are generated by impedance losses due to impedance mismatching at high frequency, and thus a new measure for basically solving the impedance problem is required.
For example, referring to FIG. 1 illustrating the architecture of a densely-integrated PCB according to the related art, in the densely-integrated PCB 100, micro-strip signal lines 120 corresponding to metal connection lines of high density which are impedance-matched with power supply lines (not illustrated) and a ground layer 110 are disposed horizontally and are responsible for horizontal transmission of signals, and vertical connection lines 130 in which the metal is filled in via-holes are responsible for vertical transmission of signals.
Then, the signals transmitted horizontally and vertically may be transmitted in the form of electrical signals which are transferred through changes in electric voltage or current. Accordingly, electrical signals using electric currents may be transferred to chips 140 mounted on a surface of the densely-integrated PCB 100 through metal wire bonding or metal solder bonding 141.
In the architecture of the densely-integrated PCB according to the related art, the electromagnetic interference (EMI) phenomenon occurs between neighboring signal lines of the micro-strip signal lines 120 and the ground layer 110, causing distortion of signals, and signal lines of another layer may act as capacitances, causing loss of signals. Then, the micro-strip signal lines 120 require impedance-matching to reduce the loss and distortion of signals. However, since the impedance is significantly influenced by the forms, such as the width, thickness, length, shape, material, or the like, of the micro-strip signal lines 120, the architecture of the densely-integrated PCB according to the related art should consider complex parameters in design of the micro-strip signal lines 120 satisfying the impedance matching.
Moreover, the impedance loss cannot be avoided fundamentally in the micro-strip signal lines 120 for high-frequency signals even though the impedance is well matched. Furthermore, for high-frequency signals the impedance matching is particularly difficult to implement in the vertical connection lines 130 through via-holes, so that much impedance loss may be generated.
Meanwhile, recently, an electromagnetic signal transmission technology which uses an electromagnetic wave tube (E-tube) for high speed data transmission through a free space between chips or boards has been suggested (Korean Patent Application No. 10-2015-0029742, PCT Application No. PCT/KR2015/005505). The E-tube is an electromagnetic signal transmission line of a tube type formed with a metal thin film surrounding a dielectric waveguide. The E-tube can be easily bent by using a flexible dielectric material and a metal thin film and thus it provides a function of signal interconnection between a transmission part and a reception part by free bending of the tube in a free space.
For example, referring to FIG. 2 illustrating a structure for transmission of electromagnetic signals between chips using an E-tube according to the related art, a substrate 210 of transmission part and a substrate 220 of reception part are disposed on a PCB 200 and a signal transmitting chip 211 and a signal receiving chip 221 are mounted on the transmission part substrate 210 and the reception part substrate 220, respectively.
Here, E-tubes 230 for transmission of electromagnetic signals are installed between the signal transmitting chip 211 and the signal receiving chip 221, and the E tube 230 is connected just above the micro-strip-to-waveguide transitions (MWTs) 212 and 222 formed on the transmission part substrate 210 and the reception part substrate 220.
The process of transmitting electromagnetic wave signals through the E-tubes 230 is as follows. Electrical signals generated by the signal transmitting chip 211 may be transmitted to the MWT 212 through a micro-strip line 213, and electrical signals transmitted to the MWT 212 may be converted into electromagnetic signals and may be transmitted to the signal receiving side through the E-tube 230. The process of receiving electromagnetic wave signals and converting the electromagnetic wave signals to electrical signals by the signal receiving side may be performed in a reverse sequence of the above-mentioned signal transmitting process.
However, in the case of transmission of electromagnetic signals between chips using the E-tubes 230 according to the related art to apply for a large-capacity system involving interconnection to other PCBs, many E-tubes 230 may be installed on the PCB 200 for interconnection to other PCBs as well as for interconnection between chips on the PCB 200 and thus the E-tubes could be complexly entangled and occupy a large space on the PCB.
Accordingly, to transmit electrical signals into the PCB, instead through a free space, a new architecture of a PCB in which electromagnetic wave transmission lines are appropriately embedded adjusting to the characteristics of the PCB is required.
Accordingly, the following embodiments of the inventive concept suggest a PCB structure having an EM-tunnel-embedded architecture and a technology of manufacturing the same, to solve the disadvantages and problems of the architecture of a densely-integrated PCB and an architecture for transmission of electromagnetic signals between chips using an E-tube according to the related art.